I don't know the exact CO policy on this (i cant imagine it allows FAs to make up their own rules), but within reason, I am OK with flight crews making up some of their own policies that clearly have our safety, security, and timeliness in mind. Obviously, having no headphones in during taxi and takeoff is important in case of emergency, and the pre-departure drinks could be a result of a slow boarding cabin or delay (hopefully not lazy crew). On the other hand, the no wine with dinner certainly does not fall under the safety and security part.